Cydia is crammed full of various themes, of which the majority are made specifically for Winterboard; and let’s face it, the most of them – barring a few exceptions – are also pretty poor. Whilst it’s nice have the capacity to add a little personal flavor proceedings, a quick check on YouTube’s array of iPhone tutorial videos suggest that tackiness often seems to prevail.

The Ultimatum theme, developed by jdsss, breaks from this mold in every way, shape and form bringing a completely new, and extremely elegant port of OS X Lion to Apple’s smartphone. Now before you write this off as just another run-of-the-mill theme, let me add that not only does it look like Apple’s desktop operating system, but it also functions as if it were a genuine version of Lion reborn for the iPhone.

Fresh out of beta stage, it accurately replicates many of your everyday OS X features, such as Finder menus, stacks, LaunchPad, scrollable docks and windows that can be dragged around as if you were using a Magic TrackPad or Mouse. Check out the video demonstration for further insight:

Despite the fact that iOS runs perfectly well as Apple’s mobile operating system, it cannot be denied that this tweak is incredibly cool. There have been many attempts, most of which have not been too successful, to port various other operating systems onto iOS. I have seen the tweak in full flow on an iPhone 3GS, and it works like a charm.

Here’s a very little guide on how you can bring Lion to your device:

Step 1: You will need to install Dreamboard, which is free on the ModMyi repo, one of the defaults unless you’ve opted to remove it.

Step 3: Whilst in Cydia still, go to the Changes tab at the bottom, and install Theme Outlet.

Step 4: Once installed, exit Cydia and open Theme Outlet which will be located on your SpringBoard.

Step 5: Within Theme Outlet, you should see the OS X Ultimatum theme. Download it.

Step 6: Finally, open Dreamboard, locate and install the theme.

And finally, as ever, you will need a jailbroken iDevice in order to enjoy a dose of OS X Lion on your iPhone, iPod touch or iPad. You can follow our step by step guide posted here to jailbreak your iPhone, iPad or iPod Touch on iOS 4.3.5 using Redsn0w (or PwnageTool), or on iOS 4.3.3 using Redsn0w, PwnageTool, Sn0wbreeze or JailbreakMe (that last one being the easiest).